@Ian84As @Mike-And-Jane0 have suggested, you can certainly use a "penalty free" cancellation option, as you are not comfortable with this reservation (assuming you have not cancelled 3 previous reservations in the last year). Keep in mind, though that "penalty free" means that you will not be financially penalized, nor have the "host cancelled this reservation" review appear. You MAY, however, find that your will lose Instant Book for a period, and future bookings for that period will all come in as requests.
Moving forward, you might wish to consider adding all of the IB requirements, such as verified id etc., that appear in your booking settings tab, if you haven't already. Be sure to also go to the "Reservation Requirements" page (which you will only find by doing a help search for "can I require guests to be verified before booking", following the link, and checking the box to require verification. This is seemingly a different requirement than what you will find in your booking settings. These additional requirements will help, but will not "guarantee" that your booking guests are who they say they are. Nothing other than personally checking identification will do that.
@Anonymousis also correct - you do NOT have to enable Instant Book to be a "superhost".